Haematoxylin

• C. I. 75290
• Natural Black 1
• Hemalum

Light-sensitive yellow solid Rauner

Fixed

~ 200 ° C ( decomposition)

Slightly soluble in water

Attention

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Hematoxylin is a natural as an ingredient of logwood ( Haematoxylon campechianum ) and related species occurring chemical compound from the groups of Indenochromene and polyphenols. It is particularly used in histology to stain of cell and tissue structures, such as nuclei, mitochondria, myelin, elastin and collagen fibers. In addition, hematoxylin found in dyeing and ink manufacturing application.

Extraction

Hematoxylin is obtained by extraction from the heartwood of Haematoxylon species. To an aqueous extract is primarily produced which is concentrated by an extraction with ether. Alternatively hematoxylin may be recovered from the aqueous extract by precipitation with urea. A synthetic preparation of hematoxylin is also described.

Chemistry

In its pure form is colorless to beige hematoxylin. By oxidation with atmospheric oxygen (slow ), or a suitable oxidizing agent (such as sodium iodate, potassium permanganate, hydrogen peroxide or iodine ) is formed in aqueous or alcoholic solution of the hematoxylin ocher colored hematein. This process is also called (natural or artificial) " maturation ". Hematein is a slightly acidic dye. The desired coloring effect is only achieved by the addition of polyvalent metal cations as a mordant. In the presence of polyvalent cations such as iron ( Fe3 ) and aluminum ( Al3 ) to dye complexes are formed by chelation in the stoichiometry of 1:1. Complexes of hematein and alums are referred to as Hämalaune. Hämalaune show the typical dark blue - violet color and are also known as Hämatoxylinlack (actually Hämateinlack ) refers.

For the preparation of dye solutions hämatoxylinhaltigen there are over 100 different recipes. Widespread use of hematoxylin Mayer, Harris, Gill ( Hämalaune ) and Weigert 's ( hematoxylin ). This color solutions contain the basic color paint in an acidic medium (pH 3-4). The connection of the ink coating to the substrate is carried in turn by chelation of polyvalent cations with anionic structures (for example, phosphate groups of the nucleic acids of the cell nucleus ). This combination of covalent and coordinate bond is stable enough to survive subsequent rinsing in water and alcohol. At the low pH of the dye solution, the stained structures appear reddish - brown, only by raising the pH by rinsing in tap water (pH 6.8-7.0 ) creates the typical blue - violet color.

By varying the pH of the selectivity for different patterns can be achieved. While at a pH value of> 4.5 number of cell structures are colored dominates at a pH of 2-3, the staining of cell nuclei.

Histology

Histology is hematoxylin for dyeing cell and tissue structures, such as nuclei, mitochondria, myelin, collagen and elastin fibers. Numerous variants of the Hämatoxylinfarblösungen have been developed, in particular, in the Hämatoxylinkonzentration, the choice of the oxidizing agent and the choice of the cation ( pickle) and thus differ in dyeing. Examples are the color solutions to Harrisburg, Honest, Mayer, Weigert, Heidenhain and Verhoeff.

Combined with the hematoxylin stain ( nuclear staining ) a counterstaining is performed with a high-contrast Zytoplasmafarbstoff generally. Classic COUNTERSTAIN with eosin performed (hematoxylin -eosin stain ), ( eg, proteins ) are stained with the cationic / eosinophilic structures. These nuclei are usually colored dark blue, while the other cell components appear light pink to pink. For HE staining Hämalaune be used. In for connective tissue ( eg, van Gieson, Masson 's trichrome ) one usually finds the Eisenhämatoxylinlösung by Weigert in combination with other acid dyes (eg Picrofuchsin, aniline blue, orange G, acid fuchsin, etc. ). For immunohistochemistry nuclear staining with hematoxylin counterstain is connected. The staining result here shows positive reactions in reddish- brown ( DAB) with soft blue nuclei.

History

The previously used in America logwood extracts were first brought by the Spanish conquistador Hernán Cortés in 1520 to Europe. The first written mention of the dye was due to Robert Hooke in 1665. Quekett (1848 ) and Waldeyer (1863 ) attributed the dye into the histochemistry. However, the results were not satisfactory, since both inserting this dye directly. The combined application still used by hematoxylin and a metal salt is due to Šumava (1865 ).